AllowPNG Property
True if PNG (Portable Network Graphics) is allowed as an image format when you save a document as a Web page. False if PNG is not allowed as an output format. The default value is False. Read/write Boolean.
Remarks
If you save images in the PNG format and if the Web browsers you are targeting support the PNG format, you might improve the image quality or reduce the size of those image files, and therefore decrease the download time.
Example
This example enables PNG as an output format for the active document.
ActiveDocument.WebOptions.AllowPNG = True
Alternatively, PNG can be enabled as the global default for the application for newly created documents.
Application.DefaultWebOptions.AllowPNG = True